The present invention relates to new dyes and to dyeing of fibers. More particularly, the invention is directed to new phosphonic acid dyes. In use, the chromophore of these new phosphonic acid dyes becomes covalently linked through a condensation residue to sites on the fiber.
Dyes are retained in fibers by physical adsorption, salt or metal-complex formation, solution, mechanical retention or the formation of covalent chemical bonds. Physical adsorption and solution, in which the dye is partitioned between the fiber and the surrounding aqueous phase, are equilibrium reactions, and only by very careful selection of the dyes used can good washfastness properties be achieved. Salt and metal complex formation are also equilibrium reactions and, though generally the retention of the dye is favored more than in physical adsorption, washfastness may still present a problem. The dyes that are held by mechanical retention (azoics, vats and sulfurs) are virtually insoluble in water and show excellent fastness to washing but have other disadvantages. They are, for example, difficult and expensive to apply; loose dye, which is not easily washed off, may be deposited on the surface, resulting in low fastness to rubbing (crockfastness), and the final shade of the dyeing does not develop until completion of the whole dyeing cycle and aftertreatments.
Chemical bonding of dye to fiber for fixation of dye was recognized as early as 1895. Reactive dye systems require that the dyes contain a functional group capable of forming a covalent chemical bond with the fiber.
Today's commercial fiber-reactive dyes are employed widely in coloring cellulosics and proteinaceous fibers. They exhibit excellent washfastness, resistance to rubbing, tinctorial powers, ease of application and leveling.
Most of the commercial systems in which today's fiber-reactive dyes are employed are based upon chemistry where the reaction is effected under alkaline conditions. Prior to applicants' aforesaid applications, there was only one such system which operated effectively at an acid pH. Such a system is desirable in the dyeing of mixed fabrics, such as cotton blends with polyester, wool or nylon, the latter two fibers being dyeable by acid dyes. However, acid dyes generally have no affinity for cellulose and usually only find use in dyeing of proteinaceous fibers.